LinearSnapHelper是Android Support库中的一个类,用于在RecyclerView中实现类似ViewPager的滑动效果。它的作用是将RecyclerView的子项对齐到RecyclerView的边缘或中心位置。
要禁用或减慢LinearSnapHelper的抛出行为,可以通过自定义一个SnapHelper的子类来实现。以下是一个示例:
import androidx.recyclerview.widget.LinearSnapHelper;
import androidx.recyclerview.widget.RecyclerView;
public class CustomSnapHelper extends LinearSnapHelper {
private static final float MILLISECONDS_PER_INCH = 100f; // 调整滑动速度的因子
@Override
public int findTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocityX, int velocityY) {
int targetSnapPosition = super.findTargetSnapPosition(layoutManager, velocityX, velocityY);
if (velocityX != 0) {
final RecyclerView recyclerView = getRecyclerView();
if (recyclerView != null) {
final RecyclerView.LayoutManager lm = recyclerView.getLayoutManager();
if (lm != null && lm instanceof RecyclerView.SmoothScroller.ScrollVectorProvider) {
final RecyclerView.SmoothScroller.ScrollVectorProvider scrollVectorProvider =
(RecyclerView.SmoothScroller.ScrollVectorProvider) lm;
final PointF vectorForEnd = scrollVectorProvider.computeScrollVectorForPosition(targetSnapPosition);
if (vectorForEnd != null) {
final int targetPosition;
if (layoutManager.canScrollHorizontally()) {
targetPosition = calculateTargetSnapPosition(layoutManager, velocityX, vectorForEnd.x);
} else {
targetPosition = calculateTargetSnapPosition(layoutManager, velocityY, vectorForEnd.y);
}
targetSnapPosition = targetPosition;
}
}
}
}
return targetSnapPosition;
}
private int calculateTargetSnapPosition(RecyclerView.LayoutManager layoutManager, int velocity, float vector) {
if (layoutManager instanceof RecyclerView.SmoothScroller.ScrollVectorProvider) {
final float millisecondsPerInch = MILLISECONDS_PER_INCH / layoutManager.getWidth();
int distance = calculateDistanceToFinalSnap(layoutManager, layoutManager.getPosition(layoutManager.getFocusedChild()));
int duration = Math.round(Math.abs(distance / vector) * millisecondsPerInch);
duration = Math.min(duration, 500); // 设置最大滑动时间为500毫秒
return velocity > 0 ? layoutManager.getPosition(layoutManager.findViewByPosition(layoutManager.getPosition(layoutManager.getFocusedChild()))): layoutManager.getPosition(layoutManager.findViewByPosition(layoutManager.getPosition(layoutManager.getFocusedChild())));
}
return RecyclerView.NO_POSITION;
}
}
在上述示例中,我们自定义了一个CustomSnapHelper类,继承自LinearSnapHelper,并重写了findTargetSnapPosition()和calculateTargetSnapPosition()方法。这两个方法用于计算滑动的目标位置和滑动的时间。
在calculateTargetSnapPosition()方法中,我们根据滑动速度和滑动方向计算出滑动的目标位置,并限制滑动时间不超过500毫秒。
然后,在使用RecyclerView时,我们可以将CustomSnapHelper设置给RecyclerView,以替代默认的LinearSnapHelper。例如:
RecyclerView recyclerView = findViewById(R.id.recyclerView);
CustomSnapHelper customSnapHelper = new CustomSnapHelper();
customSnapHelper.attachToRecyclerView(recyclerView);
这样就可以禁用或减慢LinearSnapHelper的抛出行为了。
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